Blastomere

A blastomere (plural: blastomeres ) is a cell that is formed by cleavage ( cell division by pinch ). Depending on the yolk distribution in the zygote, the blastomeres can be different sizes.

These cells do not grow at first, but become smaller with every other division. The zygote, from which extends the cleavage is, in comparison to other cells is relatively large.

At a segmentation of a isolecithalen ice (such as a sea urchin ), wherein a Radiärfurchung occurs occur differently sized blastomeres. A isolecithales egg contains little yolk evenly distributed, so this presents no obstacle to the cleavage dar. It shares the blastomere cells by size into different groups:

• The mesomeric are medium-sized blastomeres.
• The micromeres are small blastomeres. They are important for axis formation in the embryo and induce cell fates in adjacent blastomeres. Here, the transcription factor beta -catenin is important. It is located in the nucleus in micromeres and neighboring cells. Micromeres are defined by the high concentration of that substance. He gives them their inductive capacity. Core certain genes are transcribed by the beta-catenin dependent on the concentration, the products induce further developments.
• The macromers are the largest blastomeres.